MONTPELIER — It will be at least 30 days before officials at Vermont’s largest hospital know how well the transition is going to the new health insurance system that is going to start making and paying claims on behalf of patients, an official at Fletcher Allen Health Care in Burlington said Monday.

Shannon Lonergan, the director of registration at Fletcher Allen, said she anticipated some troubles in the transition, which begins Wednesday, especially from patients who have enrolled in the new health care system through the Vermont Health Connect system but have not yet received their insurance cards.

The priority for the hospital will be ensuring that patients get the care they need. And to help ease the transition to the new system the hospital will wait up to 21 days before sending bills for patients who say they have signed up for the new insurance but have no insurance cards and hospital staff can find no record of enrollment.

“I don’t know that anybody would do this for months on months on months, but I think in all fairness to the patient and the new system, this is the right approach that we’re taking. We want to make this as successful as possible for our patients,” Lonergan said.

Department of Vermont Health Access Commissioner Mark Larson said Monday the most important step people can take to ensure they’re covered is to pay their invoices as soon as possible. His office is also working with the state’s hospitals and drug stores so they will be as helpful and accommodating as possible during the transition to the new system.

For people who have chosen and confirmed their plans and received an invoice, but don’t pay their premiums before Jan. 1, their coverage will be retroactive to Jan. 1, but they could have to pay the health care provider’s bill up front and then be reimbursed by the insurance company. For January coverage people must pay their bills by the date on the invoice.

Since Oct. 1 state officials have been working to overcome problems with the Vermont Health Connect website and get as many people as possible enrolled in time to be covered by Jan. 1 while taking advantage of federal subsidies. People can still sign up.

Gov. Peter Shumlin said Monday that 22,500 Vermonters have signed up for insurance through Vermont Health Connect with about another 30,000 getting insurance directly from one of the insurance providers.

“I want to be clear: When you have 52,000 folks moving from an old system to a new system, get ready for bumps in the road,” Shumlin said.